Sewing apparatus for closing bags



Feb. 19, 1963 H. SPECK 3,077,843

SEWING APPARATUS FOR CLOSING BAGS Filed Aug. 16, 1960 e Sheets-Sheet 1 Feb. 19, 1963 H. sPEcK 3,077,843

SEWING APPARATUS FOR CLOSING BAGS Filed Aug. 16, 1960 v 6 Sheets-Sheet 2 Feb. 19, 1963 H. SPECK SEWING APPARATUS FOR CLOSING BAGS 6 Sheets-Sheet 3 Filed Aug. 16, 1960 Feb. 19, 1963 H. SPECK SEWING APPARATUS FOR CLOSING BAGS 6 Sheets-Sheet 4 Filed Aug. 16, 1960 Feb. 19, 1963 H. SPECK 3,077,843

SEWING APPARATUS FOR CLOSING BAGS Filed Aug. 16, 1960 6 Sheets-Sheet 5 L j y 28 rr-n n A 27 W 23 Fig.8

Feb. 19, 1963 H. SPECK 3,077,343

Q SEWING APPARATUS FOR CLOSING BAGS Filed Aug. 16, 1960 6 Sheets-Sheet 6 age 3,077,843 SEWING APPARATUS FUR CLQSHNG BAGS Heini Speck, Stuttgart, Germany, assignor to Union Special Maschinenfahrilt, Glacial-L, Stuttgart, Wurttemberg, Germany Filed Aug. 16, 1960, Ser. No. 59M Claims priority, application Germany Aug. 22, 195d 12 Claims. (Cl. 112-11) This invention relates to apparatus for closing bags and particularly to such apparatus which may be used in connection with automatic bag filling installations.

It is important in connection with sewing apparatus used in conjunction with automatic bag filling installations that no stoppage of the bag filling equipment is made necessary by any difiiculty encountered in the operation of the sewing apparatus. This is particularly true in situations in which stoppage of the filling equipment will interfere with the discharge of the material being packaged in a uniform condition. Such material may assume a variety of different forms, such as granules, pellets, powder and the like. Prior filling installations of this character have encountered difficulties whenever the sewing machine used for the bag closing operation has been required to be stopped due to thread breakage, needle breakage or other malfunctioning of the sewing head. Stoppage of the sewing apparatus has also been occasioned by failure of the electric driving motor for some reason. Even such prior filling installations which have been equipped with two separate sewing heads or machines on a single frame, for selective use in the closing of filled bags, have required stoppage of the sewing operation for such a period of time, measured in minutes, as to require stoppage of the filling equipment with resultant non-uniform discharge of the material into the successive bags. The filling equipment may, for example, be capable of filling about twenty bags in a minute and, therefore, if the sewing equipment is required to be stopped for as long as a minute, there will be an accumulation of non-closed bags which greatly complicates the overall operation of filling and closing a large number of bags. It is generally not possible to introduce non-closed bags into the line of filled bags approaching the sewing apparatus since such filled bags are so closely spaced as to prevent the insertion of the non-closed previously filled bags into the line.

It has been a primary object of the present invention to provide a sewing apparatus which can be kept in continuous operation in the closing of filled bags with only a few seconds delay in the sewing operation in the event of some difficulty being encountered with the sewing unit in use at a particular time. Toward this end the apparatus of the present invention is equipped with two com plete sewing units which may be selectively moved into operative position within a few seconds, thus insuring that the sewing apparatus will keep up with the filling equipment in the operation of the system as a whole. Each sewing unit has a sewing head, thread supply means and a driving motor which are ready for instant operation under the control of the operator of the equipment. The thread-carrying, stitch-forming devices of the inactive sewing unit will be properly threaded from the independent thread supply for such unit, so that the latter is ready for instant operation. Therefore, if the sewing unit under operation at a particular instant develops some defect, it is simply necessary to move this out of operative position and simultaneously move the other unit into operative position and this may be accomplished within a second or two. The two sewing units are mounted on a pedestal in such a way that they may be swung simultaneously through a suitable angle say, 180, in a horizontal direction to carry one unit from its operative position to an inoperative position and the other unit from Patented Feb. 19, 1963 its inoperative position to its operative position. The arrangement is such, moreover, that the necessary repa r of the unit which has been shifted out of operative position may be carried out without interruption of the operation of the new unit which has been swung into operative position.

In accordance with the invention, the two sewing units may be of identical form or of diiferent form. If they are of identical form, they may be adapted for the closing of either paper bags or cloth bags. Cloth bags are usually closed simply by stitching while paper bags usually require the application of a reinforcing strip along the line of stitching or a folded strip over the closed top of the bag. The sewing machines employed for the closing of the bags may be of any suitable construction, known in the art, provided with the necessary equipment for forming the type of closure desired.

The apparatus in accordance with the invention may, if desired, be provided with two different types of sewing heads such as one adapted for the closing of cloth bags and the other adapted for the closing of paper bags.

When this is done, the filling equipment may be operated without interruption to till a given quantity of one type of bag and then a desired quantity of another type of bag. The sewing units may in such a case be shifted within a few seconds to provide the desired closure for the particular bags approaching the sewing head. Also this type of apparatus will permit a quick changeover from the filling and closing of one type of bag to another, in the event of failure of the sewing unit which is in operation at any particular time.

Provision is made in accordance with the invention for very simply and rapidly varying the height of the sewing apparatus to conform with the height of the bags being filled. Preferably this is accomplished under the manual control of the operator through the operation of an electric motor. It may, however, be accomplished quite quickly by the turning of a hand crank conveniently positioned for the purpose.

A feature of t e invention is the provision of a supporting structure for the sewing apparatus which comprises two telescopically arranged tubular members which are adjustable longitudinally in relation to each other, either through the operation of the motor mentioned above or through the operation of the hand crank. A specific aspect of this phase of the invention is the provision of a sturdy but economical construction and mounting of the teiescoped tubular members. To eliminate the necessity of accurate machining of the cooperating surfaces of the two tubular members, the invention provides at least one undulated spring plate bent into substantially annular form which is disposed between the outer face of the inner tubular member and the inner face of the outer tubular member. This undulated spring member may be fitted Within a groove adjacent the top of the inner tubular member so as to-prevent movement of the plate in a direction parallel with the axis of the member. The outer tubular member, upon adjustment longitudinally in relation to the other member, slides along the undulated outer surface of the spring plate. If desired, two such spring plates may be employed, one positioned as explained above and the other fitted in a groove adjacent the lower end of the outer tubular member and slidable in relation to the outer face of the inner tubular member.

A further feature of the invention is the provision of means for preventing dirt particles and the like from entering th space between the telescopic portions of the two tubular members. The positioning of the outer tubular member at the top of the column largely achieves this purpose. However, to achieve this objective more completely, a closure member of accordion construction is provided'over the region in which the inner tubular member enters the outer tubular member. This accordion type closure has portions snugly gripping each of the tubular members and is-adapted to collapse and expand as the tubular members are shifted in relation to each other to decrease or increase the heightof the sewing apparatus in relation to the bag supporting means.

Other special features of the invention are the provision of means mounted within the hollow tubular column for varying the height of the column and other means by which the sewing heads may be simply and readily adjusted in a direction transverse to the axis of the column formed by the telescoping tubular members. This enables positioning of the sewing heads in the most desirable and efiective position in relation to the bag supporting table or conveyor system. Thus the sewing heads may. be adjusted not only vertically to accommodate bags of different heights, but also horizontally for most desirable cooperation with the tops of the bags to be closed.

' A still further feature of the invention, identified with the electrical system employed, is an arrangement of switches by which closing of the circuit through the motor which serves to increase or decrease the length of the column formed by the telescopic tubular members is prevented when either of the motors for driving the sewing heads is in operation. Also, the electrical system is provided with one control switch which serves to disconnect all of the circuits of the system from the power source and another control switch which enables the selective operation of the sewing head driving motors or their simultaneous operation. It may be desired to operate both motors when one is active in the closing of the bags and the other requires occasional operation under control of the repair man in remedying some defect in the sewingunit or its driving motor. Still another feature of the electrical system is the provision of means for opening the circuit to the motor which lifts and lowers the sewing apparatus, in the manner described, when the sewing heads reach their predetermined upper and lower limits of adjustment.

With the foregoing objects, features and advantages in view an illustrative embodiment of the invention will now be described in conjunction with the accompanying drawings, in which:

FIG. 1 is a side elevational view of the bag closing apparatus;

FIG. 2 is a plan view of the bag closing apparatus;

FIG. 3 is a horizontal sectional view taken along the line 33 of FIG. 4;

FIG. 4 is a vertical sectional view taken along the angled line 4 -4 of FIG. 3;

FIG. 5 is a view, partly in elevation and partly in vertical section, showing a portion of the supporting column and certain attachments;

FIG. 6 is an enlarged horizontal sectional view through a portion of the telescoped tubular members in the region of the undulatory spring plate;

FIG. 7 is a vertical sectional view through the upper portion of the outer tubular member showing a motor mounted thereon for varying the height of the column formed by the telesc oped members;

FIG. 8 is a view similar to FIG. 7 showing the hand crank arranged for operating the means for adjusting the height of the column; and

FIG. 9 is a circuit diagram showing the electrical connections from a power source to the various motors provided in the system.

Referring now to the drawings, the bag closing apparatusis supported by a column formed by two telescopically connected pipes or tubular members 1 and 2, the member 1 having its lower end fixed in a base 4 which may be firmly anchored to the .floor or provided with casters for readily shifting the apparatus as a whole. For carrying the filled bags to be closed there may be connected with the base 4, on a laterally extending arm thereof a table 5 or, in lieu of this, there may be provided adjacent the base 4 a conveyor belt or the like of any suitable construction. The filled bags leaving the bag filling equipment are discharged, either automatically or manually, onto the table 5 or a suitable conveyor and are shifted along the surface of the table or carried along with the conveyor belt in the course of applying the closure seam. 0f the two tubular members 1 and 2, the lower member 1 is of smaller diameter and fits within the upper member 2 in telescopic fashion, .to the extent required to position the sewing units at the required elevation for bags of the height being closed at a particular time. This arrangement, in which the upper tubular member of the column surrounds the lower tubular member thereof, largely prevents the penetration of dust and other particles into the passage between the opposed surfaces of the two members. To further guard against such penetration of dust and dirt a bellows member 16, formed of any suitable flexible material, is arranged to extend over the lower end of the upper tubular member 2 and this bellows is snugly connected at its upper end with the member 2, at a point above the lower end of said member, and at its lower end with the member 1, at a point below the lowermost position assumed by the lower end of member 2. For maintaining the two tubular members in proper relation in a manner to permit relative axial sliding thereof when it is desired to alter the overall height of the column, there is inserted between the opposed surfaces of the members one or more undulated spring elements 17 bent into a substantially annular form. As shown in FIGS. 4 and 5, one of such spring elements is fitted into an annular groove adjacent the upper end of the lower tubular member 1 and the member 2 is snugly fitted over the outwardly projecting curved portions of the undulated spring element. The relationship of the spring element to the two tubular elements is shown on a magnified scale in FIG. 6. A similar undulated spring element is preferably provided also adjacent the lower end of the tubular member 2, such spring element being fitted into an annular groove provided in the inner surface of the tube 2 and having a sliding relationship to the outer surface of tube 1. This.

arrangement insures proper alinernent of the two pipesor tubular members, permits relatively easy longitudinal movement of the tubular members in relation to each other, and eliminates the necessity of fine machine work in providing smooth surfaces of accurate dimension on the opposed faces of members 1 and 2.

On the upper tubular member 2 there is mounted a supporting frame indicated generally by the number 6 (FIG. 1) for two sewing heads 7 and 8 (FIG. 1). The frame 6 is held againstmovement longitudinally or axially of the tubular member 2 but is free to turn about the axis of the latter, as will be explained moreful-ly hereinafter. Carried by the supporting frame 6 is another frame 9 which serves as a thread stand. Frame 9 is provided with pins 11 for receiving thread cones 12 and it has an upwardly extending framework which is provided with a plurality of thread eyelets 13 for guiding the thread from the cones to the respective sewing heads. The frame 9 is of rectangular configuration in plan, as shown, and the upwardly extending portions of the frame provided with the eyelets 13 may be of similar configuration in plan. For each sewing head there are separate pins 11 and thread cones 12 for carrying the various threads required. Thus for each sewing head there may be a thread conefor needle thread, another for looper thread, and a larger cone for a filter cord commonly incorporated in a bag closing seam. One or both of the sewing heads may be provided with means for supplying a binding tape to the stitch forming point when the apparatus is being used to close paper bags. This is indicated in FIG. 1 by the provision of an inverted L-shaped rod 14 carried by the frame of the sewing unit 7 and having mounted on its horizontally extending arm a tape reel 15 from which the binding tape is fed downwardly to appropriate guiding and folding mechanism to apply the tape over the upper ends of the bag walls as these are pinched toether and to thus incorporate the tape in the bag closing seam.

On the upper end of the inner tube 1, just below the region in which the spring element 17 is located, there is provided, within the member 1, a cylindrical element 18 having a number of openings therethrough. The element 1% is held against longitudinal or axial movement in relation to the tubular member 1 in any suitable manner, as by the shoulder and snap spring ring shown in PEG. 5. At the center of element 13 there is provided a threaded bushing 1.9 which is held against rotation by screws 1% (FIGS. 1 and 4). Also the element 18 is held against turning within the tube 1 by a screw or bolt 21 (FIG. 4) secured to the tube 1 and cooperating with a vertical slot 22 in the element 18. Cooperating with the threaded bushing 19 is a threaded spindle 23 which, upon rotation in the manner to be described, serves to produce relative longitudinal movement between the tubular members l and 2, to thereby increase or decrease the length of the tubular column formed by these members. Relative turnin of the members 1 and 2 with respect to each other is prevented by a key 24 (FIG. 5) which is secured by a screw to the inner face of the member 2 and extends into a longitudinal groove 25 provided in the outer face of the member 1. As best shown in FIGS. 7 and 8, the spindle 23 is provided at its upper end with a connecting piece 26 which fits into a bushing mounted in a closure member 27 carried by the upper end of the tubular member 2. Any suitable means may be provided for retaining the connecting piece 26 against longitudinal r axial movement in relation to the bushing while permitting rotation of the connecting member in relation to the bushing. Thus, the nut applied to the upper end of the connecting piece 26 may cooperate with a washer, or plurality of washers with ball bearings therebetween, surrounding the connecting piece and resting upon the upper end of the bushing. The connecting piece 26 is adapted for connection either with a driving motor shaft 23 (FIG. 7) or with a stud 2h (FIG. 8) of a manually operative crank. It will be understood that the connecting piece 26 has a key connection with either the shaft 28 or the stud 2%. Thus, the spindle 23 may be driven either by an electric motor 47 or by a manually operated crank. As the spindle is rotated, its threaded outer surface cooperates with the internal threads of the bushing 19 and therefore serves to shift the tubular member 2 in relation to member 1 either upwardly or downwardly, depending upon the direction of rotation of the spindle 23.

While the simple, sturdy and inexpensive construction of the tubular column, formed by members 1 and 2 and the related parts described above, is particularly advantageous for use in connection with the two sewing unit construction of the present invention, it may also be used to advantage in an apparatus provided with only one sewing head which is adapted to be lifted and lowered in accordance with the length of the bags to be closed.

Secured to the closure member 27 and extending downwardly therefrom is a rod 31 (FIGS. 7 and 8) the lower end of which extends through the member 13 (FIG. and is adapted to cooperate with a pair of micro-switches one of which is indicated at 32 in FIG. 5. These switches are designated E in FIG. 9 and are for the purpose of shutting otf current to the motor i7 which, as has been explained, is used in one form of the invention for driving the spindle .23. The arrangement is such that the supply of current to the motor 47 for driving the same in one direction will be discontinued when the tubular members 1 and 2 have reached their upper limit with respect to each other, by virtue of the opening of the related switch E, even though the operator who is manually controlling the operation of the motor 47 may still be closing a switch which normally controls the operation of the motor to cause upward movement of member 2. Similarly the other switch E prevents further operation of the motor 47 in the reverse direction when the member 2 has reached its lower limit of travel. The apparatus may be so constructed as to provide for, say, a 12 relative movement of the tubular members l and 2 to provide for the closing of bags which differ to that extent in height. Of course a greater or smaller extent of relative movement of the members may be provided for, if desired. One or the other of the switches E will be opened by the rod 31 when the sewing heads reach their upper and lowermost positions.

Connected with the supporting frame 6 are two rings 33 and 34 (FIG. 4). These are interconnected by a series of members 38 which extend upwardly above the ring 34 and se ve to carry the thread stand 9 which, because of its swinging movement about the axis of member 2 along with the sewing heads and its provision of a thread eyelet for each of the threads and cords supplied to the sewing heads, serves to prevent the sewing threads and the filter cords from being entangled in the course of swinging the sewing heads to place a different one in operative position. The ring 33 has a sliding fit in relation to the tubular member 2 so as to permit it to turn freely in relation to the latter. Ring 34 is likewise free to turn about the member 2 but it is held against axial movement in relation to the latter. For this purpose it rests upon a ring 35 which is secured in any suitable way to the member 2. Ring 35 has a plurality of small openings 36 therethrough arranged to receive the lower end of a pin 3? which is slidably mounted in the ring 3 3. Pin 39 may be lifted out of engagement with the opening 35 by the clockwise movement of a lever 37 (FIG. 4) the inner end of which has a ball and socket connection with the pin 39. When the pin 39 is thus lifted, the lever 37 may be used to swing the ring 34 and the entire supporting frame 6 with its sewing heads, their driving motors and the thread stand from one position into another. As shown in FIG. 3, the swinging movement of the supporting frame and sewing heads is limited to by the cooperation of stop elements 4% and 41. It will be understood that when the parts mentioned have been swung through 180 the lever 37 will be released by the operator and the spring shown will serve to engage the lower end of the pin 39 with another opening 36 in the ring 35. This limitation of the swinging movement of the sewing heads is desirable to prevent the winding up of electric cables Within the column which would result from turning the sewing assembly through a number of revolutions around the tubular member 2.

The sewing heads 7 and 3 are provided with supporting plates 7a and 8a, respectively, which are fastened to the supporting frame 6 by means of rods 42 and 43 (FIGS. 1, 3 and 4). Each sewing head may be shifted along with its supporting plate longitudinally of the rods 42 and 43, i.e. laterally toward and away from the axis of the tubular column, and may then be locked in a set position on the rods by set screws or the like (not shown). Adjustment of the position of the sewing heads in a direction laterally of the tubular column may also be effected by shifting the rods 42 and 43 in relation to the supporting frame 6. Thus FIG. 4 shows how one of the rods 42 may be locked in set position in relation to the ring 34 by means of the bolt shown. A similar provision may be made for each of the rods 42 and 43. As will be apparent, the foregoing adjustments of the heads 7 and 8 on the rods 42 and 53 and the adjustment of these rods in relation to their carrying means permits adjustment of the sewing heads transversely with respect to a conveyor belt or a bag supporting table for proper cooperation of the sewing heads with the particular bags to be closed.

Each of the sewing heads 7 and f is provided with a separate electric driving motor, that for head 7 being indicated at 44 and that for head 3 being indicated at 45 7 (FIG.- 2). These motors are disposed diagonally opposite each on the supporting frame and are connected with their respective sewing heads by the belts shown. The motors may be-of any type conventionally employed for driving sewing machines, such as three phase asynchronous motors.

"Supporting frame 6 carries a switch box 46 (FIG. 1) containing various electrical switches, relays and the like with connections to wires which extend to the several 'it serves to select the motor 44 for operation, while when shifted to the third position, which has two contacts that may beinterconnected by the switch arm, it serves to select both motors for operation. Push button switches D (FIGS. Z and 9) are also provided at the base of the thread stand for controlling the operation of the motor 47 to bring about the upward and downward movements of the sewing heads. Motor'47 is a reversible motor, preferably of thethree phase asynchronous type.

Referring now to FIG. 9, the actual closing of the circuits'to the motors 44 and'45 is controlled by switches M and M "These are operated by relays under control of feeler controlledor manually operated switches T and F, respectively. As shown in FIG. 9, the switch S is in the position selecting the motor 45 for operation so that when the switch F is closed, the coil of relay operated switch M will be energized to draw its four armatures toward the right. The three rightmost armatures serve to complete-a circuit from switch H to motor 45 and thus bring about-operation of sewing head 8. If the arm-of switch S is shifted to the next position, towardthe right,

the motor 44 will be conditioned for operationupon the manual closing of switch T which causes the four relay operated switch arms of switch M to shift toward the right and thus complete a circuit from switch H to motor 44. The leftmost armature in each of switches M and M is arranged to prevent completion of a circuit to the motor 47 by the operation of One or another of the switches D. This is because a necessary part of the circuit completed by the closing of any of the switches D extends through the specified armatures of switches M and M This circuit may be traced from the left hand armatureof switch H to the branch line 50 immediately below the same, then through line 51 to the leftmost armature of switch M then to the leftmost armature of switch M up to the switches E, E. Assuming that these are closed and the left uppermost switch D is closed by the operator, the current'willpass through this latter switch over to the leftmost armature of the relay operated switch M then to the relay coil of switch M down to the return line of the circuit indicated in dot and dash lines. Energizing of the relayof switch M will cause the three leftmost armatures of this switch to connect the lines extending from switch H with the motor 47 for driving the latter in one direction. On the other hand, if the upper rightmost switch D is closed by the operator, the circuit will be similarly completed through the switch M since the upper right hand switchD, as shown, is in parallel with the upper left hand switch D. When it is desired to operate the motor in the opposite direction-one of the lower switches D, which are connected in parallel, must be operated. This will serve to complete the circuit through the left hand armatures of switches M and M to and through the right hand switch E to, say, the lower right hand switch D and the right hand armature of switch M to the coil of switch M down to the return line of the system. Energizing of switch M will cause its three right hand armatures "to close the circuit from the switch H to the motor=47,

but in opposite phase to the closing of such circuit by the operation of switch M As has been explained, if the sewing units happen to be at one or the other of their limits of upward and downward movement, one of the switches E will be opened and this will open the circuit through those switches D which would tend to turn the motor in the direction to cause further movement of the sewing units inthe direction which has caused the opening of the particular switch E.

It should be noted that the circuitry is such that it is not possible to close simultaneously the. necessary switches to cause delivery of current to the motor 47 for operation in both directions. This is due to the fact that when the switch M is operated, through operation ofone of the lower switches D, the leftmost armature of switch M will open the circuit necessary for the operation of switch M Similarly, when the switch M is operated, through the closing of one of the upper switches D, the right hand armature of switch M 'will open the circuit necessary for the operation of switch M As indicated schematically in FIG. 9, the SWitChT may be controlled by a feeler mechanism of any suitable character, such asthat disclosed in the Lutz ct al.Patent No. 2,932,266, granted on April 12, 1960, to bring about the closing of the switch as a filled bag approaches the stitch forming re'gionof the sewing head. Switch F may simply be manually operated. If preferred, bothswitches may be 'feeler controlled or both may be manually operated or switch F may be feeler controlled and switch T manuallyoperated, dependingupon the overall nature of the system involved in-accordance with the invention. When the switch connected with the motor of the sewing unit which is in active position is feeler controlled it will be apparent that the sewing head will be repeatedly set into operation and stopped as the filled bags advance from the filling equipment to the sewing head and as the closed bags leave the sewing head, without the necessity of the operator repeatedly operating a manual switch for this purpose.

While a preferred embodiment of the invention and various modifications thereof have been describedin considerable detail, it will be understood that various changes may be made in the construction and arrangement of the Various parts, in addition to those specifically suggested above,'without departing from the invention as defined by the appended claims.

What is claimed is:

i 1. A sewingunit. for closing filled bags comprising a supporting structure A comprising two telescopically arranged tubularmembers disposed vertically and slidable in relation to each other to vary'the overall height of said structure by varying the extent to which said members are telescoped, one of said members having a'floor engaging. part and the other of said members having means adjacent its upper end for .carryingsewing apparatus, bag supporting means disposed adjacent said floor engaging means, said apparatus comprising a plurality of sewing heads securedto said other of said members in angularly disposed relation to each other about the vertical axis of said member and so positioned as to exert balancing gravitational forces to said member, separate means for supplying thread to each of said heads and an electric motor for each of said sewing heads for operating the same, said motors being secured to said other of said members in such angularly disposed relation as to exert balancing gravitational forces to said member, connections from each of said motors to a related sewing head for'driving the latter, and releasable means for retaining said apparatus in any of a plurality of selected positions in relation to said supporting structure and enabling said apparatus to beshifted about the axis of said tubular members to position a selected one of said sewing heads in operative relation tothe topsof bags carried by said bag supporting means upon release of said releasable means, said releasable means then being adapted to retain the selected sewing head in said operative relation.

2. A sewing unit of the character set forth in claim 1 having a screw member within said tubular members, said. screw member having threaded engagement with one of said tubular members, means for retaining said screw member in fixed axial relation to the other of said tubular members, means for causing relative axial movement of said tubular members upon rotation of said screw memher, and means for turning said screw member.

3. A sewing unit of the character set forth in claim 2 having a fitting applied to said screw member which is adapted for connection either with an electric motor or a manually operable crank arm for rotation of said screw member.

4. A sewing unit of the character set forth in claim 1 in which an undulated spring element is interposed between the opposed faces of the telescoped portions of said tubular members, means being provided to prevent axial shifting of said spring element in relation to one of said tubular members.

5. A sewing unit of the character set forth in claim 4 in which said spring element is disposed within a groove provided in the outer surface of the inner tubular member adjacent the end thereof and in which another undulated spring element is provided in a groove in the inner surface of the outer tubular member adjacent the end thereof for engagement with the outer surface of the inner tubular member.

6. A sewing unit of the character set forth in claim 1 in which said means for carrying sewing apparatus comprises vertically spaced members surrounding the upper one of said tubular members for turning movement about the axis of the latter, means secured to the outer surface of said upper tubular member for supporting the upper one of said spaced members, and vertically extending members connected with each of said spaced members for retaining the same in spaced relation to each other.

7. A sewing unit of the character set forth in claim 6 in which said vertically extending members extend upwardly above the upper one of said spaced members, and

support means secured to said vertically extending members adjacent the upper ends thereof for carrying said thread supplying means for said sewing heads.

8. A sewing unit of the character set forth in claim 1 having electrical connections providing circuits from a power source to said electric motors, and a switch in said electrical connections arranged to partially complete any selected one of said circuits or all of said circuits at will.

9. A sewing unit of the character set forth in claim 8 in which a separate switch is provided in each of said circuits to the motors for selectively completing such circuits.

10. A sewing unit of the character set forth in claim 2 having an electric motor as said means for turning said screw member, electrical connections from a power source to each of said electric motors, and means in said connections for preventing operation of said motor for driving said screw member in such a direction and to such an extent as to cause lifting or lowering of said sewing units beyond predetermined limits.

11. A sewing unit of the character set forth in claim 10 having means in said electrical connections to said motor for turning said screw member for preventing operation of said screw member when any of said motors for driving the sewing units is in operation.

12. A sewing unit of the character set forth in claim 5 having a flexible bellows member surrounding said tubular members in the region in which they are telescoped, said bellows member having its upper end secured to the upper one of said tubular members and its lower end secured to the lower one of said tubular members.

References Cited in the file of this patent UNITED STATES PATENTS 1,269,727 Metz June 18, 1918 1,432,481 Mayle Oct. 17, 1922 1,719,651 Christensen July 2, 1929 2,090,587 Webb Aug. 17, 1937 2,660,140 Attwood Nov. 24, 1953 2,712,292 Kindseth July 5, 1955 2,901,992 Lutz et al. Sept. 1, 1959 

1. A SEWING UNIT FOR CLOSING FILLED BAGS COMPRISING A SUPPORTING STRUCTURE COMPRISING TWO TELESCOPICALLY ARRANGED TUBULAR MEMBERS DISPOSED VERTICALLY AND SLIDABLE IN RELATION TO EACH OTHER TO VARY THE OVERALL HEIGHT OF SAID STRUCTURE BY VARYING THE EXTENT TO WHICH SAID MEMBERS ARE TELESCOPED, ONE OF SAID MEMBERS HAVING A FLOOR ENGAGING PART AND THE OTHER OF SAID MEMBERS HAVING MEANS ADJACENT ITS UPPER END FOR CARRYING SEWING APPARATUS, BAG SUPPORTING MEANS DISPOSED ADJACENT SAID FLOOR ENGAGING MEANS, SAID APPARATUS COMPRISING A PLURALITY OF SEWING HEADS SECURED TO SAID OTHER OF SAID MEMBERS IN ANGULARLY DISPOSED RELATION TO EACH OTHER ABOUT THE VERTICAL AXIS OF SAID MEMBER AND SO POSITIONED AS TO EXERT BALANCING GRAVITATIONAL FORCES TO SAID MEMBER, SEPARATE MEANS FOR SUPPLYING THREAD TO EACH OF SAID HEADS AND AN ELECTRIC MOTOR FOR EACH OF SAID SEWING HEADS FOR OPERATING THE SAME, SAID MOTORS BEING SECURED TO SAID OTHER OF SAID MEMBERS IN SUCH ANGULARLY DISPOSED RELATION AS TO EXERT BALANCING GRAVITATIONAL FORCES TO SAID MEMBER, CONNECTIONS FROM EACH OF SAID MOTORS TO A RELATED SEWING HEAD FOR DRIVING THE LATTER, AND RELEASABLE MEANS FOR RETAINING SAID APPARATUS IN ANY OF A PLURALITY OF SELECTED POSITIONS IN RELATION TO SAID SUPPORTING STRUCTURE AND ENABLING SAID APPARATUS TO BE SHIFTED ABOUT THE AXIS OF SAID TUBULAR MEMBERS TO POSITION A SELECTED ONE OF SAID SEWING HEADS IN OPERATIVE RELATION TO THE TOPS OF BAGS CARRIED BY SAID BAG SUPPORTING MEANS UPON RELEASE OF SAID RELEASABLE MEANS, SAID RELEASABLE MEANS THEN BEING ADAPTED TO RETAIN THE SELECTED SEWING HEAD IN SAID OPERATIVE RELATION. 